1. Field of the Invention
This invention relates generally to semiconductor manufacturing, and, more particularly, to a method and apparatus for providing feedback for process control using an end of line (EOL) related parameter.
2. Description of the Related Art
The technology explosion in the manufacturing industry has resulted in many new and innovative manufacturing processes. Today's manufacturing processes, particularly semiconductor manufacturing processes, call for a large number of important steps. These process steps are usually vital, and therefore, require a number of inputs that are generally fine-tuned to maintain proper manufacturing control.
The manufacture of semiconductor devices requires a number of discrete process steps to create a packaged semiconductor device from raw semiconductor material. The various processes, from the initial growth of the semiconductor material, the slicing of the semiconductor crystal into individual wafers, the fabrication stages (etching, doping, ion implanting, or the like), to the packaging and final testing of the completed device, are so different from one another and specialized that the processes may be performed in different manufacturing locations that contain different control schemes.
Generally, a set of processing steps is performed across a group of semiconductor wafers, sometimes referred to as a lot. For example, a process layer that may be composed of a variety of different materials may be formed across a semiconductor wafer. Thereafter, a patterned layer of photoresist may be formed across the process layer using known photolithography techniques. Typically, an etch process is then performed across the process layer using a patterned layer of photoresist as a mask. This etching process results in the formation of various features or objects in the process layer. Such features may be used as, for example, a gate electrode structure for transistors. Many times, trench isolation structures are also formed across the substrate of the semiconductor wafer to isolate electrical areas across a semiconductor wafer. One example of an isolation structure that can be used is a shallow trench isolation (STI) structure.
The manufacturing tools within a semiconductor manufacturing facility typically communicate with a manufacturing framework or a network of processing modules. Each manufacturing tool is generally connected to an equipment interface. The equipment interface is connected to a machine interface to which a manufacturing network is connected, thereby facilitating communications between the manufacturing tool and the manufacturing framework. The machine interface can generally be part of an advanced process control (APC) system. The APC system initiates a control script, which can be a software program that automatically retrieves the data needed to execute a manufacturing process.
FIG. 1 illustrates a typical semiconductor wafer 105. The semiconductor wafer 105 typically includes a plurality of individual semiconductor die 103 arranged in a grid 150. Using known photolithography processes and equipment, a patterned layer of photoresist may be formed across one or more process layers that are to be patterned. As part of the photolithography process, an exposure process is typically performed by a stepper on single or multiple die 103 locations at a time, depending on the specific photomask employed. The patterned photoresist layer can be used as a mask during etching processes, wet or dry, performed on the underlying layer or layers of material, e.g., a layer of polysilicon, metal or insulating material, to transfer the desired pattern to the underlying layer. The patterned layer of photoresist is comprised of a plurality of features, e.g., line-type features or opening-type features that are to be replicated in an underlying process layer.
Turning now to FIG. 2, a flowchart depiction of an illustrative prior art process flow is depicted. A manufacturing system may determine a type of product that is to be manufactured by processing semiconductor wafers 105 (block 210). This leads to a step of determining process control parameters for processing a batch of semiconductor wafers 105. A predetermined plan for processing wafers to achieve a certain type of process result is determined. Based upon the processing plan, the manufacturing system directs various factory components to perform a series of processes upon a batch of semiconductor wafers 105 (block 220). A number of control parameters for controlling the processing of wafers are predetermined and implemented. This may include predetermined scheduling, routing, and tool control parameters to control the operations of various components of a factory or a fab.
At various points throughout the processing of the wafers, metrology data and/or tool state data may be acquired (block 230). The metrology data and/or the tool state data may be used to perform various feedback adjustments to a subsequent process step (block 240). The feedback data and/or the tool state data may be used to compensate for any detected process errors by adjusting a subsequent process. These feedback adjustments may be performed at various points in the processing stream wherein generally, feedback data is used to adjust a particular subsequent process step.
Included among the problems associated with the current metrology is the fact that various external (relative to the manufacturing area) or internal changes may cause the predetermined processing plans to become inefficient or outdated. Quite often, changes in the external factors (e.g. business factors that are not directly associated with controlling the process operations in the fab) may prompt the manufacturing system to place priority on wafers that no longer merit process priority. For example, the market climate may change after an initial assessment had indicated a demand for a particular type of product (e.g., very high speed processors), prompting demand for a second type of processor. This may make the initial processing plan less efficient.
Additionally, unexpected characteristics relating to a product manufactured by performing a series of process steps on a wafer, may call for modifications of the processes performed on other wafers. However, the requisite information required for such modifications may not be readily available until a large number of wafers have been processed. The state-of-the-art lacks an efficient methodology of anticipating potential process results and implementing modifications to a series of processes in order to preempt possible end of line deficiencies in product performance.
Furthermore, internal changes, such as changes to the operation of various processing tools, metrology tools, etc., may also cause the predetermined plan to be less than optimal. In state-of-the-art systems, changes in the factory components or external factors may not be dealt with efficiently due to the predetermined process plan that is generally used to control the process operations. Generally, a commitment to produce a particular type of process result (i.e., a particular type of integrated circuit (IC) chip) is made sometimes months in advance. These predetermined plans are then employed by through the manufacturing system. Meanwhile, various internal or external changes may occur, which may cause the predetermined plans to be no longer optimum. These changes may include changes in the market demands and/or other market forces, changes in process conditions within the factory or fab, and/or changes in the business goals of the entity performing the processes. Despite these changes, the predetermined plan is generally already implemented into processing operations and therefore, leads to a lack of flexibility in processing operations.
Designers have attempted to alleviate some of these problems by providing feedback based upon product output. However, this method does not address all of the problems described above, including changes in the business plan and/or internal factors. As an example, state-of-the-art systems generally call for adjusting the same process, or the next process, based upon the reception of a process feedback signal that is received from a downstream process. This adjustment may not be enough to address all of the issues relating to end-of-line product data. Additionally, various external factors, such as market changes and business goals may not be efficiently addressed by such state-of-the-art systems. This could lead to inefficient reaction to various internal or external factors, leading to a loss of reaction time to a business factor and/or lack of flexibility in adjusting for internal manufacturing problems.
The present invention is directed to overcoming, or at least reducing, the effects of one or more of the problems set forth above.